Casing for electric shot-firing machines



1935. K. SCHAFFLER-GLCSSL 1,990,279

CASING FOR ELECTRIC SHOT FIRING MACHINES Filed Nov. 18, 1933 FIG. 1. 12

Patented Feb. 5, 1935 PATENT OFFICE casino roa ELECTRIC SHOT-FIRING momsKonrad Schafller-Gliissl, Vienna, Austria Application November 18 3Claims.

This invention relates to an improved protective casing for electricshot-firing machines for use in connection with blasting work in mines,and has for its object to provide a light weight casing 01 this naturehaving a reliably'tight joint between 'the cover and the main bodyportion thereof. Further objects of the invention will become clear inthe course of the ensuing description. The essential feature of theinvention consists in the fact that the lid of the casing consists oftwo sheets of metal disposed one above the other and at a distance fromeach other, so that they form between them the groove for the groovejoint between the cover and the body of the casing.

It is already known to manufacture a protective casing consisting of abody portion and a cover, for portable electric shot-firing machines foruse in mines where there is danger of firedamp explosion, of metalcastings, and to effect a tight joint between the casing proper and theedge of the cover by a groove-joint.

If it is desired to avoid the obvious disadvantage of castings, whichconsists in their heavy weight conditioned by relatively greatwall-thickness, and to make both casing and cover of sheet metal it isno easy matter to obtain a groove-joint which is comparable ineffectiveness to that obtainable when the parts are cast. It is in factpossible, with a sheet metal cover having a downwardly extending flangeadapted to fit over the upper edge of the main body of the casing, toprovide a jointing groove by the arrangement of a second flange which isdisposed parallel to the said first flange and distanced therefrom tothe extent of the thickness of the upper rim of the main body 01 thecasing, and which is attached to the cover for example by rivets orsoldering. Such an attachment, however, apart from the fact that it iscomplicated and expensive in manufacture, would not provide withreliability the degree of tightness required as a precaution against thedanger from firedamp, and would also not satisfy the requirements of themore recent mine regulations.

The difliculty here involved is overcome, in accordance with theinvention, by making the cover of two similarly shaped parts which arearranged in spaced relation one above the other, and which arepreferably made of drawn sheet metal. The edges of these parts areflanged or turned over, so that they together form the groove for thereception 01' the rim of the main body of the casing. These turned-overflanges fit tightly against both sides of the edge of the casing overtheir entire length, when the cover is placed in position on 1933,Serial No. 698,733 Germany November 18, 1932 the main body of thecasing, with the result that long leakage paths are formed which checkthe intrusion of explosive gases, and prevent by cooling the blowingpast of the flame of any gas happening to become ignited.

A constructional example embodying the invention is shown, by way ofexample, in the accompanying drawing, in which:

Fig. 1 is a longitudinal section of a shot-firing machine provided witha protective casing accordl0 ing to the invention.

Fig. 2 is a plan view of the casing, showing the cover, and theapertures therein.

Referring to the drawing, in Fig. 1 the casing and cover which enclosethe shot-firing machine proper, and which are the subject of the presentinvention are rendered prominent by being drawn in heavier lines. In thedrawing 1 denotes the main body of the casing, 2 and 3 the two parts,respectively, of the cover, 4 and 5 the flanged edges of the latter and6 the upper edge of the main body of the casing.

A tight joint is formed between the body 1 of the casing and thetwo-part cover by the insertion of a packing in the groove, againstwhich the upper edge 6 of the body is pressed by tensioning or stressingmeans of a known type, such as for example the screw 9 and the lugs 7and 8. The mode of construction of the lid or cover in accordance withthe invention makes it possible to provide this packing in aparticularly convenient and suitable manner in a continuous piecefilling out the narrow space between the two parts 2 and 3 of the coverand extending up to the head of the jointing groove. This packing isdenoted by the reference number 10. This arrangement has the particularadvantage that the packing can not fall out of the groove as isotherwise the case with packings inserted in grooves.

Packing can also be provided in a similar manner for the parts of thefiring machine projecting through the cover, such as the boss 11 of thewinding-up pin 12, the insulation body for the lead-in terminals 13, andthe like, the arrangement being that one or both of the parts of thecover are flanged up at these points, and made to fit closely with theirflanged edges 14 and 15 about the parts concerned. In this manner longleakage paths are formed which effectually prevent the intrusion ofexplosive gases into the casing at these points.

An additional packing of these joints can also be provided by theprovision of inserted packing material. For this purpose the flanged rim16 of the outer sheet of the cover can for example be inwardly bent overat right angles, and a packing 18 provided between the ring 17 thusformed and the edge of the flanged rim 14. The pressure required forforcing this packing into close fitting contact both with the boss 11 ofthe winding-up pin and with the edges 14 and 17, and also the pressurerequired for holding together the two sheets forming the cover, issupplied by known means, in the present instance for example by means ofthe nut 19 pertaining to the firing machine, so that no special meansneed be provided for this purpose.

What I claim is: V

1. A casing for an electric shot-firing machine comprising a main bodyportion, and a cover consisting of two superposed substantially similarsheet metal parts having bent-over outer edges in parallel spacedrelation and adapted to contact closely throughout their entire widthwith the inside and outside surfaces of the top of the said body portionthroughout the entire peripheral length thereof, for the purpose ofensuring that the said cover be explosion-proof, readily removable, ofgreat rigidity, and of light weight.

2. A casing for an electric shot-firing machine comprising a main bodyportion, a cover consistlength thereof.

3. A casing for an electric shot-firing machine comprising a main bodyportion, a cover consisting of twosuperposed substantially similar sheetmetal parts having bent-over outer edges, apertures in the said coverfor projecting elements pertaining to the said machine, the edges of thesaid cover parts adjacent the said apertures being upwardly flanged incontiguity with each other and I with the said elements, an inwardlyturned rim on the upwardly flanged edge of the outer of the said coverparts, and a packing element between the said rim and the upper edge ofthe upwardly flanged edge of the inner of the said cover parts,

KONRAD scHAFFLER-Gwssn

